The present invention relates to a liquid crystal display apparatus, and particularly relates to a liquid crystal display apparatus provided with a plurality of pixels.
Since a liquid crystal display apparatus has such features as light weight, compact size and low power consumption in comparison with a CRT (Cathode Ray Tube), it is used in various types of electronic device as a display. A liquid crystal display apparatus displays an image by changing an orientation of liquid crystal molecules aligned in a predetermined direction by an electric field and controlling the amount of light transmission through a liquid crystal layer.
A liquid crystal display apparatus has a pair of substrates including, for example, an array substrate and a color filter substrate. In the array substrate, for example, thin film transistor (TFT) as switching elements are formed in an array so as to correspond to each of the pixels of the liquid crystal display apparatus. In the color filter substrate, color filters are formed so as to correspond to each of the pixels of the liquid crystal display apparatus. A liquid crystal layer is filled in a space between the array substrate and the color filter substrate, and an electric field applied to the liquid crystal layer is changed by switching the TFT in each pixel.
As a method of applying an electric field to a liquid crystal layer, the method utilizing a vertical electric field scheme and the method utilizing a lateral electric field scheme have been known.
In the liquid crystal display apparatus employing the lateral electric field scheme, for example, on a liquid crystal layer side of either one of a pair of substrates including an allay substrate and a color filter substrate, a pair of electrodes are provided so as to be insulated from each other, and an approximately lateral electric field is applied to the liquid crystal molecules. As the liquid crystal display apparatus employing the lateral electric field scheme, the apparatus of an IPS (In-Plane Switching) mode in which the pair of electrodes is not overlapped with each other when seen in a plan view and the apparatus of an FFS (Fringe Field Switching) mode in which the electrodes are overlapped with each other have been known.
Of these, in the liquid crystal display apparatus of the FFS mode, paired electrodes including a common electrode and a pixel electrode are each disposed on respectively different layers via an insulating film, a slit-like aperture is provided in the common electrode or the pixel electrode on the liquid crystal layer side, and an approximately lateral electric field passing through this slit-like aperture is applied to the liquid crystal layer. Since the liquid crystal display apparatus of the FFS mode has such effects of wide viewing angle and improved image contrast, it has been used more in recent years.
In each of various types of liquid crystal display devices including such a liquid crystal display device of the FFS mode, surfaces of a scanning line, a signal line and a TFT formed on an array substrate are covered with an interlayer resin film, and a pixel electrode is formed on the interlayer resin film. Moreover, a contact hole that penetrates the interlayer resin film to reach a drain electrode of the TFT is formed on the interlayer resin film, and the pixel electrode and the drain electrode are electrically connected with each other via the contact hole. Furthermore, a light-shielding unit is formed on a portion between pixels on a liquid crystal layer side of a color filter substrate.
Japanese Patent Application Laid-Open Publication No. 2001-174844 (Patent Document 1) and Japanese Patent Application Laid-Open Publication No. 2001-272698 (Patent Document 2) have described a technique in which, by forming a pixel electrode after forming a contact hole that penetrates an interlayer resin film on a drain electrode to reach the drain electrode, the pixel electrode and the drain electrode are electrically connected with each other.